In many of present hybrid vehicles, an inverter has a large box-shaped casing fixed to a chassis, and a motor casing (transaxle) is arranged under the casing. When consideration is given to the drive device for a hybrid vehicle that can be mounted in as many types of vehicles as possible, it is difficult for the configuration having two casing to standardize parts of the device, since optimum arrangement of these casings is performed for each type of the vehicle.
In principle, it is desired that the units to be combined for operation are accommodated in one casing and are integrated with each other. Japanese Patent Laying-Open No. 2004-343845 (which will be referred to as the “Patent Document 1” hereinafter) has disclosed a drive device for a hybrid vehicle having a motor and an inverter integrated with each other. In the Patent Document 1, a structure includes a drive device casing formed of a plurality of casing portions that are coupled together and accommodate electric motors, respectively, and a plurality of inverters corresponding to the respective electric motors. In this structure, the plurality of inverters are collectively arranged in one of the above casing portions, and fluid passages for cooling the inverters are formed between the casing portion provided with the inverters and the respective inverters. The above structure can integrate the inverters corresponding to the respective electric motors with the drive device and further can achieve inverter cooling.
However, in the drive device casing disclosed in Japanese Patent Laying-Open No. 2004-343845 (Patent Document 1), the casing portions accommodating the respective motors are coupled to the casing portion accommodating the inverter. Therefore, in the structure of the drive device for the hybrid vehicle disclosed in the Patent Document 1, electromagnetic noises caused by a switching operation of a power element in the inverter are liable to leak through a coupling portion where the above casing portions are coupled together. Therefore, countermeasures must be taken to prevent leakage of the electromagnetic noises through the coupling portion where the casing portion of the inverter is coupled to the other portions. If the countermeasures are insufficient, leaked electromagnetic noises may adversely affect other equipment on the vehicle.
Since the inverter is simply arranged on the motor in the above structure, the structure is susceptible to improvement in connection with a vertical position of a center of gravity of the vehicle carrying the drive device. Further, sufficient consideration is not given to reduction in space required in the hybrid vehicle for arranging the drive device. For allowing mounting of the drive device on many kinds of vehicles, it is desired that the inverters and the motors are arranged in a contour substantially equal to that of an automatic transmission that neighbors to an engine in an ordinary vehicle.